The bulk of the world's liquid petroleum resources are located in heavy oil and oil sand reservoirs. While some of this resource can be recovered by highly geotolerant recovery processes such as mining, these procedures are typically only economic for shallow resources, are very costly, produce high carbon dioxide emissions, use large volumes of water, and incur other environmental penalties. Most of the world's heavy oil and bitumen resource is buried too deeply to mine economically and so in situ recovery methods utilizing boreholes predominate. Conventional in situ recovery of viscous and poor quality oils currently relies on either primary production, as in cold heavy oil production, or thermal and/or solvent based methods to mobilize the oil by reducing its viscosity. Analysis of the variability of the petroleum resource may often necessitate sampling reservoirs samples at high frequency.